Uninteresting parameters

Most aspects of destructuring are supported in parameter lists:
* rest parameters
* destructuring of individual parameters
However, there is at least one aspect which is not, which is
uninteresting parameters :
[x, , z] = arr;
which for parameter lists would look like:
function(x, , z) {...}
This could be useful when you are a defining a callback which needs to
match a certain signature, but you only care about a certain subset of
the arguments not at the beginning. For example:
function evens(arr) {
arr.filter(function(,index) {return index % 2});
}
However, I admit it can look strange especially when the uninteresting
parameter is at the beginning as in the above example.
Thanks,
Sean Eagan